it really depends on what you have to spend.
also, my reccommendations are based on my own assumptions of what you have, which is a completely stock 69 302 2v, that is in good running condition with not a ton of miles or hard wear on it. which is what i started with in my 69
if you are running stock then you likely have some restrictions to think about. like ignition. probably ignition being the first most restrictive. Becuase if you are running points in tyour distributor you are going to drop hp at and after 4,000 rpms.
I would start with a pertronix module for a starter. they are fairly inexpensive and will allow you to use hp past 4,000 rpms when you start modding things.
here is one on ebay to give you an idea.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7970064606&category=33691
it also would not hurt to replace your coil and cap and wires while you are at it.
If you are still with the stock 2v carb setup. then you can't go wrong with a good edelbrock performer intake and something like a 600cfm 4v carb. i went with the edelbrock 600.
but if you have the money to spend, you might was well replace the heads with something like the edelbrock performer heads. (i know i sound like an edelbrock rep, but i just like them becaue they are good and not too pricey for me) with the carb and intake, it would not be unheard of to expect a 50hp gain from adding these heads.
after the heads you should contact someone like comp cams with your engine set up and have them reccommend a custom cam that will compliment what you have.
at this point, you should consider adding some headers and exhaust that will flow well enough for your better breathing engine.
it is tough and inacurate to guess hp on paper, but with these mods above. i think you could bring the stock rated 220hp 302 you have in your car to the 300-335hp range without breaking a sweat. probably quite a bit more, but i try to stay on the conservative side of the fence when guessing at hp.
these mods are about as far as you will want to go with stock pistons and rods.
expect all these mods to cost you in the $3,000 area
my .02
